Psychopaths are responsible for a disproportionate amount of crime. These people are primarily identified by an extreme lack of empathy. Now a study finds that when psychopaths see images of people in pain, there’s a pattern of activity in their brains that is quite different from brain activity in non-psychopaths.

Researchers tested 80 prisoners to gauge their levels of psychopathy. They then scanned the prisoners’ brains using functional MRI as the prisoners were shown photos of people being intentionally hurt.

Participants who scored high in psychopathy traits, versus those who were not considered psychopaths, showed much less activation in the areas of the brain involved in emotional reactions, social behavior and decision making. The study is published in the journal JAMA Psychiatry.

Unexpectedly, when viewing the photos the psychopaths experienced significant activity in the insular cortex, which is involved in emotion and self-awareness. The researchers conjecture that the reaction may have been due to the prisoners ability to imagine themselves in pain. In a still unpublished study with other inmates, subjects were specifically told to imagine the painful event happening to someone else. In that case, those scoring high in psychopathy had a lesser reaction. The psychopath thus seems able to relate to pain—as long as it’s his own.

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